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Magnetochemistry, Volume 7, Issue 10 (October 2021) – 8 articles

Cover Story (view full-size image): The known scope of transition-metal compounds that undergo spin crossover (SCO) is overwhelmingly dominated by complexes of the Fe(II) ion in octahedral coordination of six N-donor atoms. The discovery of SCO behavior in novel coordination environments promises to offer new opportunities for the design of materials and devices that rely on spin-state switching. To that end, we demonstrate the usefulness of S-coordinating ligands for the synthesis of SCO complexes and compare the relative strength of topologically similar tetradentate ligands with the {N4} and {N2S2} coordination environments.View this paper
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Review
Magnetic Functionalization of Scanning Probes by Focused Electron Beam Induced Deposition Technology
Magnetochemistry 2021, 7(10), 140; https://doi.org/10.3390/magnetochemistry7100140 - 13 Oct 2021
Cited by 1 | Viewed by 957
Abstract
The fabrication of nanostructures with high resolution and precise control of the deposition site makes Focused Electron Beam Induced Deposition (FEBID) a unique nanolithography process. In the case of magnetic materials, apart from the FEBID potential in standard substrates for multiple applications in [...] Read more.
The fabrication of nanostructures with high resolution and precise control of the deposition site makes Focused Electron Beam Induced Deposition (FEBID) a unique nanolithography process. In the case of magnetic materials, apart from the FEBID potential in standard substrates for multiple applications in data storage and logic, the use of this technology for the growth of nanomagnets on different types of scanning probes opens new paths in magnetic sensing, becoming a benchmark for magnetic functionalization. This work reviews the recent advances in the integration of FEBID magnetic nanostructures onto cantilevers to produce advanced magnetic sensing devices with unprecedented performance. Full article
(This article belongs to the Special Issue Advances in Magnetic Force Microscopy)
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Article
Magnetic Properties of a Ni Nanonet Grown in Superfluid Helium under Laser Irradiation
Magnetochemistry 2021, 7(10), 139; https://doi.org/10.3390/magnetochemistry7100139 - 11 Oct 2021
Viewed by 895
Abstract
A nanonet consisting of ultrathin Ni nanowires (diameter <4 nm) and Ni nanoballs (diameter <20 nm) has been grown through laser ablation of a Ni target in superfluid helium. At a low Ni concentration, the nanonet consists mainly of nanowires and manifests a [...] Read more.
A nanonet consisting of ultrathin Ni nanowires (diameter <4 nm) and Ni nanoballs (diameter <20 nm) has been grown through laser ablation of a Ni target in superfluid helium. At a low Ni concentration, the nanonet consists mainly of nanowires and manifests a rectangular magnetic hysteresis loop, while an increase in the Ni concentration results in an increase in both the concentration and diameter of the nanoballs. A decrease in hysteresis loop rectangularity is observed as the concentration of the nanoball increases. We show that the composition of the system can be determined from the changes in the magnetic hysteresis loop and the temperature dependence of magnetization. The significance of the work consists of the observation of evolution of magnetic properties of the ferromagnetic nanonet, while its composition varies from nanowires to a combined nanowires–nanoballs system. Full article
(This article belongs to the Special Issue Soft and Hard Magnetic Materials: Latest Advances and Prospects)
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Review
The Underexplored Field of Lanthanide Complexes with Helicene Ligands: Towards Chiral Lanthanide Single Molecule Magnets
Magnetochemistry 2021, 7(10), 138; https://doi.org/10.3390/magnetochemistry7100138 - 09 Oct 2021
Cited by 1 | Viewed by 799
Abstract
The effective combination of chirality and magnetism in a single crystalline material can lead to fascinating cross-effects, such as magneto-chiral dichroism. Among a large variety of chiral ligands utilized in the design and synthesis of chiral magnetic materials, helicenes seem to be the [...] Read more.
The effective combination of chirality and magnetism in a single crystalline material can lead to fascinating cross-effects, such as magneto-chiral dichroism. Among a large variety of chiral ligands utilized in the design and synthesis of chiral magnetic materials, helicenes seem to be the most appealing ones, due to the exceptionally high specific rotation values that reach thousands of deg·cm3·g−1·dm−1, which is two orders of magnitude higher than for compounds with chiral carbon atoms. Despite the sizeable family of transition metal complexes with helicene-type ligands, there are only a few examples of such complexes with lanthanide ions. In this mini-review, we describe the most recent developments in the field of lanthanide-based complexes with helicene-type ligands and summarize insights regarding the further exploration of this family of compounds towards multifunctional chiral lanthanide single molecule magnets (Ln-SMMs). Full article
(This article belongs to the Special Issue Reviews on Slow-Relaxation Molecules)
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Article
A Quantum-Mechanical Study of Antiphase Boundaries in Ferromagnetic B2-Phase Fe2CoAl Alloy
Magnetochemistry 2021, 7(10), 137; https://doi.org/10.3390/magnetochemistry7100137 - 09 Oct 2021
Cited by 1 | Viewed by 736
Abstract
In this study, we performed a quantum mechanical examination of thermodynamic, structural, elastic, and magnetic properties of single-phase ferromagnetic Fe2CoAl with a chemically disordered B2-type lattice with and without antiphase boundaries (APBs) with (001) crystallographic orientation. Fe2CoAl was modeled [...] Read more.
In this study, we performed a quantum mechanical examination of thermodynamic, structural, elastic, and magnetic properties of single-phase ferromagnetic Fe2CoAl with a chemically disordered B2-type lattice with and without antiphase boundaries (APBs) with (001) crystallographic orientation. Fe2CoAl was modeled using two different 54-atom supercells with atoms on the two B2 sublattices distributed according to the special quasi-random structure (SQS) concept. Both computational models exhibited very similar formation energies (−0.243 and −0.244 eV/atom), B2 structure lattice parameters (2.849 and 2.850 Å), magnetic moments (1.266 and 1.274 μB/atom), practically identical single-crystal elastic constants (C11 = 245 GPa, C12 = 141 GPa, and similar C44 = 132 GPa) and auxetic properties (the lowest Poisson ratio close to −0.1). The averaged APB interface energies were observed to be 199 and 310 mJ/m2 for the two models. The studied APBs increased the total magnetic moment by 6 and 8% due to a volumetric increase as well as local changes in the coordination of Fe atoms (their magnetic moments are reduced for increasing number of Al neighbors but increased by the presence of Co). The APBs also enhanced the auxetic properties. Full article
(This article belongs to the Special Issue Ferromagnetism)
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Review
Resonant Soft X-ray Reflectivity in the Study of Magnetic Properties of Low-Dimensional Systems
Magnetochemistry 2021, 7(10), 136; https://doi.org/10.3390/magnetochemistry7100136 - 07 Oct 2021
Cited by 1 | Viewed by 716
Abstract
In this review, the technique of resonant soft X-ray reflectivity in the study of magnetic low-dimensional systems is discussed. This technique is particularly appealing in the study of magnetization at buried interfaces and to discriminate single elemental contributions to magnetism, even when this [...] Read more.
In this review, the technique of resonant soft X-ray reflectivity in the study of magnetic low-dimensional systems is discussed. This technique is particularly appealing in the study of magnetization at buried interfaces and to discriminate single elemental contributions to magnetism, even when this is ascribed to few atoms. The major fields of application are described, including magnetic proximity effects, thin films of transition metals and related oxides, and exchange-bias systems. The fundamental theoretical background leading to dichroism effects in reflectivity is also briefly outlined. Full article
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Article
Magnetic Field Perturbations to a Soft X-ray-Activated Fe (II) Molecular Spin State Transition
Magnetochemistry 2021, 7(10), 135; https://doi.org/10.3390/magnetochemistry7100135 - 02 Oct 2021
Cited by 2 | Viewed by 887
Abstract
The X-ray-induced spin crossover transition of an Fe (II) molecular thin film in the presence and absence of a magnetic field has been investigated. The thermal activation energy barrier in the soft X-ray activation of the spin crossover transition for [Fe{H2B(pz) [...] Read more.
The X-ray-induced spin crossover transition of an Fe (II) molecular thin film in the presence and absence of a magnetic field has been investigated. The thermal activation energy barrier in the soft X-ray activation of the spin crossover transition for [Fe{H2B(pz)2}2(bipy)] molecular thin films is reduced in the presence of an applied magnetic field, as measured through X-ray absorption spectroscopy at various temperatures. The influence of a 1.8 T magnetic field is sufficient to cause deviations from the expected exponential spin state transition behavior which is measured in the field free case. We find that orbital moment diminishes with increasing temperature, relative to the spin moment in the vicinity of room temperature. Full article
(This article belongs to the Section Spin Crossover and Spintronics)
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Article
Pyridyl-Thioethers as Capping Ligands for the Design of Heteroleptic Fe(II) Complexes with Spin-Crossover Behavior
Magnetochemistry 2021, 7(10), 134; https://doi.org/10.3390/magnetochemistry7100134 - 01 Oct 2021
Cited by 1 | Viewed by 798
Abstract
Mononuclear heteroleptic complexes [Fe(tpma)(bimz)](ClO4)2 (1a), [Fe(tpma)(bimz)](BF4)2 (1b), [Fe(bpte)(bimz)](ClO4)2 (2a), and [Fe(bpte)(bimz)](BF4)2 (2b) (tpma = tris(2-pyridylmethyl)amine, bpte = S,S′-bis(2-pyridylmethyl)-1,2-thioethane, bimz = 2,2′-biimidazoline) were [...] Read more.
Mononuclear heteroleptic complexes [Fe(tpma)(bimz)](ClO4)2 (1a), [Fe(tpma)(bimz)](BF4)2 (1b), [Fe(bpte)(bimz)](ClO4)2 (2a), and [Fe(bpte)(bimz)](BF4)2 (2b) (tpma = tris(2-pyridylmethyl)amine, bpte = S,S′-bis(2-pyridylmethyl)-1,2-thioethane, bimz = 2,2′-biimidazoline) were prepared by reacting the corresponding Fe(II) salts with stoichiometric amounts of the ligands. All complexes exhibit temperature-induced spin crossover (SCO), but the SCO temperature is substantially lower for complexes 1a and 1b as compared to 2a and 2b, indicating the stronger ligand field afforded by the N2S2-coordinating bpte ligand relative to the N4-coordinating tpma. Our findings suggest that ligands with mixed N/S coordination can be employed to discover new SCO complexes and to tune the transition temperature of known SCO compounds by substituting for purely N-coordinating ligands. Full article
(This article belongs to the Special Issue Stimuli-Responsive Magnetic Molecular Materials)
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Review
Magnetic Nanomaterials as Biocatalyst Carriers for Biomass Processing: Immobilization Strategies, Reusability, and Applications
Magnetochemistry 2021, 7(10), 133; https://doi.org/10.3390/magnetochemistry7100133 - 23 Sep 2021
Cited by 1 | Viewed by 1174
Abstract
Environmental concerns, along with oil shortages, have increased industrial interest in biomass conversion to produce biofuels and other valuable chemicals. A green option in biomass processing is the use of enzymes, such as cellulases, hemicellulases, and ligninolytic (laccase and peroxidases), which have outstanding [...] Read more.
Environmental concerns, along with oil shortages, have increased industrial interest in biomass conversion to produce biofuels and other valuable chemicals. A green option in biomass processing is the use of enzymes, such as cellulases, hemicellulases, and ligninolytic (laccase and peroxidases), which have outstanding specificity toward their substrates and can be reused if immobilized onto magnetic nanocarriers. Numerous studies report the biocatalysts’ performance after covalent binding or adsorption on differently functionalized magnetic nanoparticles (MNPs). Functionalization strategies of MNPs include silica-based surfaces obtained through a sol–gel process, graphene oxide-based nanocomposites, polymer-coated surfaces, grafting polymer brushes, and others, which have been emphasized in this review of the immobilization and co-immobilization of enzymes used for biomass conversion. Careful analysis of the parameters affecting the performance of enzyme immobilization for new hybrid matrices has enabled us to achieve wider tolerance to thermal or chemical stress by these biosystems during saccharification. Additionally, it has enabled the application of immobilized laccase to remove toxic organic compounds from lignin, among other recent advances addressed here related to the use of reusable magnetic carriers for bioderived chemical manufacturing. Full article
(This article belongs to the Special Issue Magnetic Properties of Nanomaterials)
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